Process of producing wood preservative



Patented May 13, 1941 UNITED STATE PATENT OFFICE PROCESS OF PRODUCING WOOD PRE SERVATIVE No Drawing. Application December 18, 1939, Serial No. 309,897

10 Claims.

This invention relates to the production of Wood preservatives from tars and fractions thereof and comprises a continuation in part of my co- .pending application Serial No. 235,897, filed October 19, 1938.

An objectof the invention is the production of specification wood preservatives from starting materialsnottotally acceptable as-wood preservatives, said starting materials including various tars, high boiling fractions and pitches derived therefrom.

A further object of the invention is to provide a process for subjectingof starting tar fractions susceptible to preferential hydrogenation, to the action of hydrogen or hydrogen-containing gases, including steam, while in the presence of fractions less susceptible to' hydrogenation, whereby to reduce the residue above 355 C. andto induce toxicity in the resultant material.

A further object of the invention is the providing of excess hydrogen or hydrogen-containing gases, including steam, whereby to provide sufiicient reacting material to secure full efiect on those fractions susceptible to preferential hydrogenation while acting to some extent on other fractions.

(Either objects of the present invention will be apparent from the following disclosures.

In theart of wood preservation, tars derived from coal, Wood and petroleum comprise by far the largest group of starting materials for the, preparation of wood preservatives, and among this group coal tar is the most important. The following examples will indicate coal tar or fractions thereof as the starting materials, though in no sense is the selection of, said materials as examples to be construed as limitations.

Coal tar, commonly referred ,to as coke oven tar has, per se, excellent wood. preserving qualitiesas regards its toxicity, but several of its characteristics, as for instance high residue above 355 (3., high coke residue, high insolubility in benzol or the like and high viscosity, make it not acceptable as a wood preservative in some fields.

Such coal tar may be refined as by distillation to recover an oilcreosote--which has a permissible coke residue, viscosity, loW boiling fractions, residue above .355 C., and specific gravity, as for instance comparable to American Wood Pre- I servers Association specifications for grade 1 creosote as follows:

1. The oil shall be a distillate of coal-gas tar or coke-oven tar. It shall comply with the following requirements:

. It shall not contain more than 3% of water.

. It shall not contain more than 0.5% of matter insoluble in benzol.

4. The specific gravity of the oil at 38 0., compared with water at 155 C..sha1l be not less than 1.03.

5. The distillate, based on water-free oil, shall be within the following limits:

Up to 210 0., not more than Up to 235 0., not more than 6. The residue above 355 C., if it exceeds 5%, shall have a float test of not more than seconds at C.

7. The oil shall yieldnot more than 2% of coke residue.

8. The foregoing tests shall be made in accordance with the standard methods of the American Wood Preservers Association.

CADN

ass

on distillation not more than 3% should pass at 150 C., 10% at 200 C., 25% at 235 C; (bulb in vapor) Distillation recovery of the above named creosotes from tarleaves in the still a residue, pitch, which is at times a seriously distress product. It therefore is a desideratum in the art to provide a process which produces or secures from coal tar a larger percentage of wood preservative, as for instance the creosote above specified, or any other grade of preservative desired by the consumer.

Treating average tars for distillation recovery of creosote results generally in from 25%65% being recovered as a distillate. When as little as 25% is recovered as a distillatecreosotethe grade of said. creosote is acceptable, however the economic ill obtains that of. the tar must be marketed as pitch, which, as stated, is a product greatly distress at times. When recovering as high as 50%-65% as creosote, the resultant pitch is of a low grade and the creosote is so high in residue above 355 C. that it is not acceptable to many users who demand a low residue creosote. A common demand is for a creosote having %25% residue above 355 C.

It is found that the various creosotes produced, reflect to a certain extent in their price structure the distress condition of pitch.

To enable consumers of wood preservatives derived from tar to purchase usable preservatives at a lower cost, tar refiners market products known as 80-20 oil, 70-30 oil, 50-50 oil, etc. which refers, as in the first illustration, to 80% creosote and tar. The thus produced 80-20 oil can be sold at a price lower than the creosotes as is obvious. However, by marketing such an oil, the distiller or refiner does not entirely eliminate the distress condition of pitch, for the reason that the 80% creosote that entered the 80-20 oil has, as a natural sequence, the production of aforesaid distress pitch.

A generally accepted specification for 80-20 oil is the A. W. P. A. specification referred to as Dewey S47, Class 5d, as follows:

1. The solution shall be a coal tar product of which at least 80% shall be'of coal gas tar or coke oven tar, and the remainder shall be refined or filtered coal-gas tar or coke oven tar. It shall comply with the following requirements:

2. It shall not contain more than 3% of water. water.

3. It shall not contain more than 2% of matter insoluble in benzol.

4. The specific gravity of the solution at 38 C. compared with water at 15.5 C. shall not be less than 1.4)5 or more than 1.12.

5. The distillate, on a water-free basis, shall be within the following limits: Up to 210 0., not more than 5%; up to 235 0., not more than 6. The solution shall yield not more than 6% coke residue.

7. The foregoing tests shall be made in accordance with the standard methods of the American Wood Preservative Association (see Manual- Creosote, analysis).

Thus it will be seen that a greater recovery of specification creosote from tar is to be desired. Economics considered, the United States yearly produces an amount of coal tar, which if distilled, would yield an amount of specification creosote which would make this country self-suflicient in its annual creosote requirements. However, because the tar refiner must confine the amount of creosote he produces to the corresponding amount of pitch he can market, this country annually imports many millions of gallons of creosote. Such a fact is borne out by an address given by no less an authority than S. P. Miller, Technical Director, The Barrett Co., New York, before Franklin Institute in December 1932. Conditions in the coal tar industry have not materially changed since 1932, in that pitch continues as a distress product.

By the process of the present invention tar in itsoentirety maybe converted, transformed, reformed, modified or treated to provide a wood preservative of predetermined specifications acceptable in the light of present specifications or specifications that may later be made.

- As far as applicant understands the theory thereof, the present invention is predicated on the following:

First, that'there are fractions of tar having an inordinate aflinity for hydrogen, and that the saturation, partial saturation, reforming, converting, or modifying of these fractions to provide additional low boiling fractions induces toxicity;

Second: That the change brought about by the process of the invention, in the material, be it full or partial saturation, reformation, conversion, or modification, which provides additional low boiling fractions also lowers the coke residue, residue above 355 0., specific gravity and viscosity;

Third: To accomplish the results described there must b present not only extraneous gas, including steam, but the gas must be present in excess of the amount actually entering into the combination with the fractions having inordinate affinity for hydrogen as well as with those having less afiinity; and

Fourth: The fractions upon which preferential hydrogenation is most marked are the ones outside the range generally depended upon for toxic action, and therefore which it is particularly desirable to have improved in this respect.

The present invention may be viewed as including a process for converting tar in its entirety to a wood preservative of superior toxicity and of any desired specifications by treatment which tends to promote the condition of saturation, partial saturation or reformation of the various fractions and which induces new toxic fractions boiling below 270 C. at the expense of fractions formerly boiling above that temperature. The treatment also reduces residue above 355 C.

In the application for my Patent No. 2,125,918 I stated that the toxicity of wood preservative is proportional to the percentage thereof bolling below 270 C. and further that in the hydrogenation of a mixture of coal tar fractions the action of hydrogenation is preferential upon the higher boiling fractions. I have now discovered that when the reaction is properly controlled the preferential action of hydrogen does not correspond to an even curve of increase as the boiling point rises but that the action is more pronounced upon the fractions boiling at or above 270 C. The result of this phenomenon is that when the mixture of hydrocarbon fractions is treated with hydrogen, those most in need of beneficiation and having initially the least toxicity are as surely chosen out for improvement as though the material were fractionated before treatment and those needing the treatment were treated separately.

Mention has been madeof the production of wood preservatives suitable as substitutes for -20, 70-30, 50-50 oil etc. In the following tabular data is shown the Variations in the end product that may be had when practicing the present invention.

The tabular data show that the present invention may be practiced so as to vary the percentage of toxicity induced in the material boiling below 270 C., also as to vary the percent-age of reduction in residue above 355 C., coke residue and specific gravity.

In all the tabular data cited, the starting material is identical and the inspection of same is noted under Pilot Analysis; columns listed as #1 impression, #2 impression, etc. are for the purpose of showing how toxicity, residue above 355 C., coke residue and specific gravity may be varied by impressing control conditions on the starting material ranging from vigorous to less vigorous-#1 impression is the most vigorous shown, #2 impression less vigorous, etc., the change from each to the next being in the activity of the catalyst. The numbers opposite the boiling operation, into a usable wood preservative having enhanced toxic values, as compared with the parent material; and with, the added advantage that no pitch is produced to burden the already ranges are percentages of the whole. glutted pitch market.

Pilot analy- #1 im- #2 im- #3l'm- #4im- #5 im- #(iim- #7in1- #8 im- #9 im- #10 im- #llim- #12 im- SIS, pres- Dl'eS- DFQS- DiQS presprespresprespres- DFBS- pres- DTP/S- ig? SlOIl S1011 S1011 S1011 S1011 S1011 S1011 S1011 510D SiOll SlOIl S1011 8:85 1255 12:50 11:90 13:60 11:0 12:6 12:3 123 1213 11:4 1213 1112 8:33 12.05 10.0 10.90 10.50 10.7 10.4 11.3 10.1 10.3 10.3 10.3 9.9 3%? 12 28 i8 i8 a: 11 n 21 Residue 54Is0 44151 47150 47140 450 48150 4610 4511 4811 4815 4613 40I1 5010 The starting material, at each impression was Example 2.The process of the present invenheld 130 a temperature of Q, pressure of 200 tion is especially applicable to the treating of atmospheres, and the hydrogen flow was at the tars, or fractions thereof, in more than one conrate of 20,000 cubic feet per barrel of feed; time verting treatment. For instance, a tar having a of ea ti n u cat yst, moly d um s coke residue of 16.4, s ecific gravity r 1.16, and phde. l 1 C H h 107 v d less than 35% distilling at 355 C. is subjected to ramp 6 0a a1 avlng a cone resi 116, 25 the action of in excess of 5000 cubic feet of hyboiling at 3 C. a d oo reat viscosity for drogen per barrel tar in the presence of a catausei as].O 8 10100?) lirese gi'gt vg a d g s i g ytg lyst while under superatmospheric pressure and en s 01 mg e 0W 15 S J m e at 400 C. The fractions boiling above 270 C. gggenciof fa ctatglyist to the action 0? more tll' llain 30 were preferentially hydrogenated, and toxicity 011 0 8 y roger! pe one W 18 was added to theproduct.

heated to from 300 to 600 C. a d under p From the process control just stated flowed a atmosph ric p essure for s ha length of e a beneficiated tar, which after being relieved of 0 preferentially p o e an mofioilnate Percent? its excess gaseous material, was found to have age of ftratctloni bo t i p 0 These are 3 in addition to increased toxicity, lowered viscose mos 0X1c 910 O S- 0 ity, specific gravity and a coke residue not in t his p c fi r ag a w s excess of 12. The thus treated material was J S 9 0 one 9 ene e are again processed in accordance with controls set after being relieved of its excess gaseous material, f rth in the first part of the present example h d a e residue less than 7 less then 2 The twice beneficiated tar was found to have still g gg j kglbw (1 t gh i ft ii g l 40 further increased toxicity, lowered viscosity, spe- & a vlscosl Y ma 9 1 5a cific gravity, residue above 355 C. and coke as a coal tar-creosote solution, such as 80-20 011 residue, and to be u f l for many purposes to g 3- -t T 1 p4 Oduct 15 more toxlc than the which conventional creosote or creosote-coal tar 5 ma ena solutions have former] been ut.

Y controliingfhe heajt and pressur? with the Instead of using the twice beneficiated tar en 9 f i f 2 9 f toto as the wood preservative, the material may lavlflg an lflor 1; or i be distilled to yield desired specification oil with 101 61 ?1 y st mtm yt 6 re Qfi 1; 1 the residue discarded or forming starting mate- ?h is cczig e g Z :3g g m rial for another cycle as previously mentioned.

I O 7 sote-ccal tar oil of any grade as so zo, 70 30, or .1 terms desmd f tf and eve a 991 or 1 99 on and an every cas will be fspecification \goodtprelservatnile as used 1n the v oregomg may em erc angea e. 2 12352552?tiifi silitiit ttt iitii than time Slightly atmospheric to w h L carry the process of the present invention forg g iizifig i gigggg fi 22 33:: ward, but elevated pressures are preferred, and E i reforming 3 conversion less Thus may be as high. as securable. It is desirable that the pressure be sufficient to hold at least 50% of 2 33 5 :31; iggg gg g f g g gg iggg figgggz the material in the liquid phase. Temperatures as low as 200 C. are usable, but the time eleg zg z g figg ggf g g gf g izggg i ment islengthened, thus it becomes preferred to to roduce a Wood preservatvive acceptable as a use higher temperatures (but not usually in ex.- subgtitute for 80 20 30 etc 011 cess of 600 C.), in order that the time may be when practicing the process a percentage shgrhtgrgg-e element is difilcult toexpress in terms of low-boiling oil not permissible is formed, th of (infinite limits. some staytmg materials unwanted materal may be stripped and discarded th f I k f r as the usage as a wood preservative is Spend 0 8 pre f cpnvdswl? more qmc mso 1y than others; too, it may be required to have a gg aggressionpreferentiallyhydmgenated more pronounced preferential hydrogenation in is meant that the fraction of tar so designated is some. cases i m i l dependent upvon the hydrogenated to a greater degree or extent than star t'1ng material and deslrsd end f other fractions when practicing the controls fth Periods shorter than an hour are usable, while pmcess as set forth By controlling the process for some cases one or more hours are required. as stated, and using tar as a starting material, It has been defimt'ely shown, however that 7 control over processing conditions of tar or fracthe tar en toto is converted by aonce through tions thereof as specified in the foregoing, which results in the preferential saturation, partial saturation, reforming, transforming, or converting of the fraction above 270 C., induces toxicity, lowers coke residue, residue above 355 C., specific gravity and viscosity and falls within the purview of the present invention.

Usable catalysts are those adapted to effect saturation, partial saturation, reforming or converting action and may be deposited on various shapes and sizes of inert carriers, as for instance silica gel, or the catalyst may be Without inert carrier.

Especially are those catalysts usable that are substantially immune to sulphur poisoning, such as sulphides of heavy metals, also molybdenum, tungsten, chromium and uranium. Other catalysts immune to sulphur poisoning may also be used, or more than one catalyst at the same time or successively, or mixtures of such catalysts with other bodies. Other compounds acting in a different manner, as for example splitting agents, and inert solid bodies may also be added. Alumina and silica, cobalt and manganese, separately or in admixture, supported or unsupported may be used. Difficultly reducible oxides of various metals, with or without conversion to sulphides are also usable.

The presence of quartz, asbestos, coke, activated carbon, heavy metals or metal oxides, alone or in admixture tends to reduce coke formation.

The hydrogen bearing gas may be activated by flowing the same over the catalyst before passing the gas to the treating chamber, in order to avoid fouling a catalyst.

The present invention is not restricted in its scope to the impressing of specified conditions on any of the starting materials whereby to form "specification wood preservatives, but broadly includes the inducing of toxicity in mixtures of tar fractions comprising at least in considerable proportions those found in commercial tar, by impressing on said starting material specified control to induce preferential saturation, partial saturation, reforming, converting or transforming especially of the fractions boiling above 270 Thus, the saturation, partial saturation, as for instance by hydrogen or the like, conversion, transformation or treatment of tars or fractions thereof, by the process as stated whereby to produce preferential saturation, partial saturation, conversion .or transformation of the fractions boiling above 270 0., and to induce toxicity, reduce coke residue, residue above 355 C., viscosity and specific gravity, falls entirely within the teaching of the present invention even though present-specification wood preservative is not formed, for the reason that the present invention is concerned especially, among other things, with the stated novel manner of inducing toxicity, regardless of present wood preservative specifications.

Tars and fractions thereof may be treated by the process of the present invention to induce toxicity as described, and to lower coke residue, without producing a wood preservative meeting current specifications, yet providing a product usable as a wood preservative which because of its increased toxic value, reduced coke residue, specific gravity and viscosity may be used in the art as wood preservative and may come to be a basis for future accepted trade specifications.

For instance, a coke oven tar may be processed in accordance with the present invention to produce a substitute for a creosote-coal tar solution oil, as for instance an -20 oil or the like; toxicity is induced for reasons above stated, yet the coke residue, etc. may not be acceptable under current specifications. Such a condition, however, does not preclude the use of said product as a wood preservative inasmuch as its toxicity and general characteristics make it suitable for such use, and which sooner or later will be recognized and specifications drawn to allowuse of said product as stated.

As stated in the foregoing, fractions other than the ones boiling above 270 C. partake in the saturation, partial saturation, transformation or conversion of the present invention, however to a lesser degree. The benefits flowing from the present invention, including increased toxicity, fiow as a result of that control which preferentially beneficiates the fractions boiling above 270 C.

Impressing of the stated conditions on any of the starting materials produces, other things being equal, a beneficiation in toxicity proportional to the time element; however an inordinate length of time, as will be found by trials, at times produces low boiling ends not desired in the wood preservative.

If and when low boiling ends of non-permissible nature are produced they may be stripped and discarded insofar as use as a wood preservative is concerned. Too vigorous conditions as produced by heat may also produce unwanted low boiling ends. These may be discarded as noted, or they may be allowed to remain.

A tar may be found to have so high a percentage of objectionables as to be not convertible to the specification demanded by straight treatment by the process herein-before described. By objectionables is meant coke residue, free carbon, insolubles in benzol or other non-volatile substances difiicult or impossible of conversion. In this event the process may proceed as follows:

Example 3.-The tar is tested to determine what amount of said objectionables must be removed to bring the percentage thereof in the whole batch down to that which is permissible, andsuch an amount of tar is segregated from the batch as will contain the ascertained amount of objectionables. The segregated material is evaporated to dryness and the vapors are condensed and returned to the parent batch. A material will then be had which may be treated as herein disclosed to give a solution to comply with the demanded specification.

The process of the present invention involving preferential action with marked emphasis on the fractions at and adjacent to the 270 C. boiling point is of value in the production of creosote as well as in the production of creosote-coal tar solution oil. To take advantage of the principle in creosote production, the tar may first be subjected to treatment with hydrogen bearing gas under the conditions named for preferential action on fractions boiling about 270 0., thus lowering the boiling point of fractions which otherwise would go to the pitch if the tar had not been pretreated. Because of the principle enunciated little if any of the low boiling fractions will be moved down into the range too light for creosote.

The thus treated tar may then be distilled in the usual creosote-producing manner. Study of the tabulated data above given will show that in the case of the #399 tar there treated, and with a fresh catalyst as in impression #1, a once through treatment left less than 5% boiling below 210 C. which is permissible under current creosote specifications. If the treated material of impression #1 is distilled to 355 C. to strip creosote, 12.3% more creosote would be secured than if the untreated material had been strippedwith a correspondingly less residue of pitch. The creosote so secured would be in greater yield than a comparable cut on the raw material.

Viewed broadly, current coal tar wood preservative specifications stem from, among other things, the characteristics of tar that the refiner is economically justified in selling as a wood preservative. Thus when a new wood preservative processed from coal tar as starting material, and having excellent qualities and serving to relieve distress conditions in coal tar products is produced, specifications may, other things being equal, be rewritten to conform to the new wood preservative.

Minor changes may be made in the steps of the process within the scope of the appended claims without departing from the spirit of the invention.

I claim:

1. In the enhancement of toxicity induction in a mixture of tar fractions boiling preponderantly above 270 C., the process which comprises: subjecting said mixture of tar fractions to the action of a supply of hydrogen in excess of that combinable by the process, at a temperature in excess of 200 C. and a pressure in excess of atmospheric; carrying on the process for such a length of time as to provide fractional increti.

ment having increased toxic properties and boiling below 270 C. in excess of fractional increment having increased toxic properties and boiling above 270 C.

2. The process of claim 1 with inclusion of the step of stripping from the treated mixture of tar fractions any percentage of low boiling fractions not permissible in a specification Wood preservative.

3. The process of claim 1 with inclusion of the step of distilling the treated mixture of tar fractions to recover a wood preserving distillate of enhanced toxicity.

4. The process of claim 1 with the inclusion of the step of distilling the treated mixture of tar fractions to recover a wood preserving distillate of enhanced toxic value, and removing from said distillate any percentage of low boiling ends to provide conformance in initial boiling point to specification wood preservatives.

5. In the enhancement of toxicity induction in a mixture of tar fractions at least once refined by hydrogen, said mixture of tar fractions boiling preponderantly above 270 C. the process which comprises: subjecting said mixture of tar fractions to the action of a supply of hydrogen in excess of that combinable by th process at a temperature in excess of 200 C. and a pressure in excess of atmospheric; carrying on the process for such a length of time as to provide fractional increment having increased toxic properties and boiling below 270 C. in excess of fractional increment having increased toxic properties and boilingabove 270 C.

6. The process of claim 5 with inclusion of the step of stripping from the treated mixture of tar fractions any percentage of low boiling fractions not permissible in a specification wood preservative.

7. The process of claim 5 with inclusion of the step of distilling the treated mixture of tar fractions to recover a wood preserving distillate of enhanced toxicity.

8. The process of claim 5 with the inclusion of the step of distilling the treated mixture of tar fractions to recover a Wood preserving distillate of enhanced toxic value, and removing from said distillate any percentage of low boiling ends to provide conformance in initial boiling point to specification wood preservatives.

9. The process of claim 1 in which the hydrogen supply is in excess of 3,000 cubic feet per barrel material treated.

10. The process of claim 5 in which the hydrogen supply is in excess of 3,000 cubic feet per barrel material treated.

JACQUELIN E. HARVEY, JR. 

